The invention relates to a device for fluid treatment, in particular for waste-water treatment, wherein the fluid is led along or through at least one surface coated with material.
Such devices are known in the prior art, be they in the form of filters which hold back particles of a certain size, or in the form of biological fluid treatment devices, with which a fluid is led along a surface coated with micro-organisms. Such a device is known, for example, from International application publication No. WO 02/094724 A1.
Irrespective of whether the fluid to treated is guided through or along a surface, problems occur with continuous operation, to the extent that the flow resistance increases due to a clogging of the permeated surface or due to a growth of the coated surface. It is therefore necessary to carry out a cleaning at regular intervals, in order to reduce the flow resistance. With filters, this is typically accomplished by way of back-flushing, or by way of mechanical removal of the particles, but has the disadvantage that the method takes its course in a discontinuous manner, and the flow resistance increases between the individual cleaning cycles, i.e. is thus not constant.
With devices for biological fluid treatment, it is furthermore necessary to remove the microorganisms sticking to the surface, only inasmuch as they are superfluous, since the continued presence of microorganisms is absolutely necessary for the continued, effective fluid treatment. With the device known from WO 02/094724 A1, this is achieved in that the disk stacks which mesh with one another almost contact one another in partial regions of radial webs, so that these webs constantly remove the material coating of the opposite disk over the whole surface. An accumulation may therefore essentially only occur in the recessed regions between the webs, whereby the active surface of the disks is reduced. A further disadvantage of this arrangement is the fact that only the excess of the grown-on microorganism material is removed, whereas no renewal is effected in the base, which may lead to the device losing its efficiency in the course of time.